Browsing by Autor "Matthias Schleuning"

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Bracken fern facilitates tree seedling recruitment in tropical fire-degraded habitats
(Elsevier BV, 2014) Silvia C. Gallegos; Isabell Hensen; Francisco Saavedra; Matthias Schleuning
Deforested habitats lack seeds of late‐successional and large‐seeded plant species in tropical montane forests
(Wiley, 2015) Francisco Saavedra; Isabell Hensen; Matthias Schleuning
Abstract Questions (1) How do seed density and species richness of late‐successional, pioneer and non‐forest species change from forest interior to deforested habitats? (2) Are seed density and species richness of seed species dispersed into deforested areas enhanced by perch structures? (3) Do morphological seed traits of forest and non‐forest plant species change from the forest interior to deforested areas? Location Deforested tropical mountains of Chulumani, La Paz, Bolivia. Methods At eight study sites, we installed a system of 38 seed traps along a transect of 240 m from the forest interior (160 m from the forest margin) toward deforested areas (80 m from the forest margin). Half of the seed traps installed in the deforested areas were positioned under perch structures. We identified captured seeds to morpho‐species or species level and recorded morphological seed traits (i.e. seed mass, seed length, seed width) and species origin (i.e. late‐successional, pioneer, non‐forest species). Results Seed density and species richness of late‐successional and pioneer species declined from the forest interior toward deforested areas. Seed limitation was particularly strong for large‐seeded species. Perches in deforested areas strongly increased the density and to some extent as well as the species richness of seeds dispersed into these areas, but did not alter the composition of seed traits and species origin in comparison to seed traps without perches. Conclusions We found a strong seed dispersal limitation in deforested areas, which was mitigated by the presence of perch structures, at least in terms of seed density and species richness. However, the dispersal limitation of late‐successional plant species with large seeds was not compensated by the presence of perching structures. Nevertheless, the establishment of artificial perch structures is likely to be a promising strategy for capturing seeds in deforested areas that may establish under bracken fronds in the long term.
Differences in bird and bat traits, seed-dispersal interactions and functions between tropical montane forest and bracken-dominated areas
(Frontiers Media, 2025) César Mayta; Matthias Schleuning; Cecilia L. López; Mariana Villegas; Isabell Hensen; Silvia C. Gallegos
Most tropical plant species depend on animals to disperse their seeds. Seed dispersal by animals allows plants to colonize new sites in deforested habitats helping to accelerate forest recovery. However, deforestation can affect the interactions between animals and plants that are crucial for forest regeneration. In this study, we analyze the differences on the composition of functional traits and on seed-dispersal interactions and functions by birds and bats between forest and deforested areas dominated by bracken fern. At eight study sites, we captured birds and bats in bracken-dominated areas and at forest in the tropical montane forest of Bolivia and analyzed their droppings. We found a similar composition of functional traits related to animal size, gape width and degree of frugivory of bats in both habitat types. Hand-wing index of birds was significantly higher in bracken compared to forest. Birds had more interaction richness and abundance in bracken than in forest, and bats had more interaction abundance in forest than in bracken. The majority of seeds dispersed by birds and bats in bracken were from pioneer species. We conclude that, although seed dispersal by birds and bats is maintained in the bracken-dominated areas, most of the dispersed seeds belong to pioneer species. Pioneer species are unlikely to establish in bracken-dominated areas, making the natural regeneration process of these deforested areas very slow.
Effects of disturbance and altitude on soil seed banks of tropical montane forests
(Cambridge University Press, 2013) Denis Lippok; Florian Walter; Isabell Hensen; Stephan Beck; Matthias Schleuning
Abstract: Vast areas of tropical forests have been deforested by human activities, resulting in landscapes comprising forest fragments in matrices of deforested habitats. Soil seed banks (SSB) are essential sources for the regeneration of tropical forests after disturbance. In a fragmented montane landscape in the Bolivian Andes, we investigated SSB in three different habitat types that were associated with different degrees of disturbance, i.e. in forest interior, at forest edges and in deforested habitats. Sampling of habitats was replicated at six sites ranging in altitude from 1950 to 2450 m asl. We extracted seeds from dried soil samples by sieving, classified seeds into morphospecies and size classes, and characterized SSB in terms of density, species richness and composition. We tested effects of disturbance (i.e. habitat type) and altitude on SSB characteristics. Overall, small seeds (<1 mm) dominated SSB (81% of sampled seeds). Seed density and species richness were lowest in deforested habitats, especially in large seeds and distant from adjacent forests (≥20 m), while small-seeded species were most numerous near forest margins. Species turnover between habitats was high. Altitude altered the composition of SSB, but had no effects on seed density and species richness. We conclude that the potential of SSB for natural regeneration of deforested habitats is low and decreases with increasing distance from forest remnants and that forest edges may be eventually invaded by small-seeded species from deforested habitats.
Elevation, Topography, and Edge Effects Drive Functional Composition of Woody Plant Species in Tropical Montane Forests
(Wiley, 2015) Amira Apaza‐Quevedo; Denis Lippok; Isabell Hensen; Matthias Schleuning; Sabine Both
Abstract Tropical montane forests comprise heterogeneous environments along natural gradients of topography and elevation. Human‐induced edge effects further increase the environmental heterogeneity in these forests. The simultaneous effects of natural and human‐induced gradients on the functional diversity of plant leaf traits are poorly understood. In a tropical montane forest in Bolivia, we studied environmental gradients associated with elevation (from 1900 m to 2500 m asl), topography (ridge and gorge), and edge effects (forest edge vs. forest interior), and their relationship with leaf traits and resource‐use strategies. First, we investigated associations of environmental conditions (soil properties and microclimate) with six leaf traits, measured on 119 woody plant species. Second, we evaluated changes in functional composition with community‐weighted means and functional structure with multidimensional functional diversity indices ( FR ic, FE ve and FD iv). We found significant associations between leaf traits and soil properties in accordance with the trade‐off between acquisition and conservation of resources. Functional composition of leaf traits shifted from the dominance of acquisitive species in habitats at low altitudes, gorges, and forest interior to the dominance of conservative species in habitats at high altitudes, ridges, and forest edges. Functional structure was only weakly associated with the environmental gradients. Natural and human‐induced environmental gradients, especially soil properties, are important for driving leaf traits and resource‐use strategies of woody plants. Nevertheless, weak associations between functional structure and environmental gradients suggest a high redundancy of functional leaf traits in this tropical montane forest.
Factors limiting montane forest regeneration in bracken-dominated habitats in the tropics
(Elsevier BV, 2016) Silvia C. Gallegos; Stephan Beck; Isabell Hensen; Francisco Saavedra; Denis Lippok; Matthias Schleuning
Forest fragmentation and edge effects on the genetic structure of<i>Clusia sphaerocarpa</i>and<i>C. lechleri</i>(Clusiaceae) in tropical montane forests
(Cambridge University Press, 2013) Amira Apaza‐Quevedo; Matthias Schleuning; Isabell Hensen; Fransisco Saavedra; Walter Durka
Abstract: Fragmentation of tropical forests influences abiotic and biotic processes that affect the genetic structure of plant populations. In forest fragments, edge effects, i.e. changes of abiotic and biotic factors at forest edges, may be prevalent. In two forest fragments ( c . 200 ha at c . 2450 m asl) of tropical montane forest in Bolivia, sympatric populations of the dioecious tree species Clusia sphaerocarpa and C. lechleri were used as case study species to compare genetic diversity and small-scale genetic structure (SGS) between edge and interior habitats. Eight microsatellite markers were employed to genotype 343 individuals including adults, juveniles and seedlings of C. sphaerocarpa and 196 of C. lechleri . Genetic differentiation was found between habitats in both species (Φ RT = 0.071 for C. sphaerocarpa and Φ RT = 0.028 for C. lechleri ) and among ages in C. sphaerocarpa (Φ RT = 0.016). Overall, SGS was weak but significant with more pronounced SGS in C. lechleri ( Sp = 0.0128) than in C. sphaerocarpa ( Sp = 0.0073). However, positive spatial genetic autocorrelation extended only up to 10 m. For C. sphaerocarpa , SGS was stronger in seedling and juvenile stages than in adults and in the forest interior than at forest edges. Our results show that edge effects can extend to the genetic level by breaking-up local genetic structures, probably due to increased gene flow and enhanced pollination and seed-dispersal interactions at forest edges.
Forest recovery of areas deforested by fire increases with elevation in the tropical Andes
(Elsevier BV, 2013) Denis Lippok; Stephan Beck; Daniel Renison; Silvia C. Gallegos; Francisco Saavedra; Isabell Hensen; Matthias Schleuning
Functional importance of avian seed dispersers changes in response to human-induced forest edges in tropical seed-dispersal networks
(Springer Science+Business Media, 2014) Francisco Saavedra; Isabell Hensen; Stephan Beck; Katrin Böhning‐Gaese; Denis Lippok; Till Töpfer; Matthias Schleuning
Human-Induced Disturbance Alters Pollinator Communities in Tropical Mountain Forests
(Multidisciplinary Digital Publishing Institute, 2012) Stephan Kambach; Fernando Guerra; Stephan Beck; Isabell Hensen; Matthias Schleuning
Mountain forest ecosystems in the Andes are threatened by deforestation. Increasing fire frequencies lead to fire-degraded habitats that are often characterized by a persistent fern-dominated vegetation. Little is known about the consequences of these drastic changes in habitat conditions for pollinator communities. In a rapid diversity assessment, we collected individuals of two major groups of insect pollinators (bees and butterflies/moths) with pan traps and compared pollinator diversities in a spatial block design between forest interior, forest edge and adjacent fire-degraded habitats at eight sites in the Bolivian Andes. We found that bee species richness and abundance were significantly higher in fire-degraded habitats than in forest habitats, whereas species richness and abundance of butterflies/moths increased towards the forests interior. Species turnover between forest and fire-degraded habitats was very high for both pollinator groups and was reflected by an increase in the body size of bee species and a decrease in the body size of butterfly/moth species in fire-degraded habitats. We conclude that deforestation by frequent fires has profound impacts on the diversity and composition of pollinator communities. Our tentative findings suggest shifts towards bee-dominated pollinator communities in fire-degraded habitats that may have important feedbacks on the regenerating communities of insect-pollinated plant species.
Secondary dispersal by ants promotes forest regeneration after deforestation
(Wiley, 2014) Silvia C. Gallegos; Isabell Hensen; Matthias Schleuning
Summary Many remnants of tropical forests are surrounded by deforested areas dominated by successional vegetation. Although secondary dispersal by scatter‐hoarding rodents and ants may influence seed predation and seedling recruitment, very little is known about its importance in degraded forest ecosystems. We studied the effects of secondary dispersal on seed predation, germination and seedling recruitment of the primarily bird‐dispersed tree C lusia trochiformis in a tropical montane forest in B olivia. We carried out exclosure experiments that allowed or excluded access to seeds by vertebrates in three habitat types (forest interior, degraded habitat close to and degraded habitat far from the forest margin) in a spatial block design at six sites. We offered a total of 1440 seeds (both with and without an aril) and marked half of them with a thread to follow their fate after 48 h and after 1 month. We found that secondary dispersal by ants was highest in the forest interior but was also frequent in degraded habitats close to and far from the forest edge. Secondary dispersal significantly increased seedling recruitment, particularly in the degraded habitats, probably because seeds were often dispersed to sites beneath the leaf litter. Recruitment success increased significantly with dispersal distance. High recruitment of secondarily dispersed seeds in the degraded habitat was due to the combined effect of reduced predation and increased germination of seeds that had been moved by ants. Synthesis . In the absence of secondary dispersal, seed germination and seedling recruitment were very low in degraded habitats. Seed dispersal by ants substantially increased natural regeneration in the deforested habitats. Our experiments thus demonstrate that the effects of biotic interactions on plant demography can vary across habitat boundaries at small spatial scales and that secondary dispersal is a crucial and overlooked process that can aid the regeneration of deforested habitats in the tropics.
Seed-deposition and recruitment patterns of Clusia species in a disturbed tropical montane forest in Bolivia
(Elsevier BV, 2017) Francisco Saavedra; Isabell Hensen; Amira Apaza‐Quevedo; Eike Lena Neuschulz; Matthias Schleuning
Specialists and generalists fulfil important and complementary functional roles in ecological processes
(Wiley, 2021) D. Matthias Dehling; Irene M. A. Bender; Pedro G. Blendinger; Katrin Böhning‐Gaese; Marcia C. Muñoz; Eike Lena Neuschulz; Marta Quitián; Francisco Saavedra; Vinicio Santillán; Matthias Schleuning
Abstract Species differ in their resource use and their interactions with other species and, consequently, they fulfil different functional roles in ecological processes. Species with specialized functional roles (specialists) are considered important for communities because they often interact with species with which few other species interact, thereby contributing complementary functional roles to ecological processes. However, the contribution of specialists could be low if they only interact with a small range of interaction partners. In contrast, species with unspecialized functional roles (generalists) often do not fulfil complementary roles but their contribution to ecological processes could be high because they interact with a large range of species. To investigate the importance of the functional roles of specialists versus generalists, we tested the relationship between species' degree of specialization and their contribution to functional‐role diversity for frugivorous birds in Andean seed‐dispersal networks. We used two measures for the specialization of birds—one based on the size, and one based on the position of their interaction niche—and measured their effect on the birds' contribution to functional‐role diversity and their functional complementarity, a measure of how much a species' functional role is complementary to those of the other species. In all networks, there were similar log‐normal distributions of species' contributions to functional‐role diversity and functional complementarity. Contribution to functional‐role diversity and functional complementarity increased with both increasing niche‐position specialization and increasing niche size, indicating that the composition of functional roles in the networks was determined by an interplay between specialization and generalization. There was a negative interaction between niche‐position specialization and niche size in both models, which showed that the positive effect of niche‐position specialization on functional‐role diversity and functional complementarity was stronger for species with a small niche size, and vice versa. Our results show that there is a continuum from specialized to generalized functional roles in species communities, and that both specialists and generalists fulfil important functional roles in ecological processes. Combining interaction networks with functional traits, as exemplified in this study, provides insight into the importance of an interplay of redundancy and complementarity in species' functional roles for ecosystem functioning. A free Plain‐Language Summary can be found within the Supporting Information of this article.
Topography and edge effects are more important than elevation as drivers of vegetation patterns in a neotropical montane forest
(Wiley, 2013) Denis Lippok; Stephan Beck; Daniel Renison; Isabell Hensen; Amira Apaza‐Quevedo; Matthias Schleuning
Abstract Aims The high plant species diversity of tropical mountain forests is coupled with high habitat heterogeneity along gradients in elevation and topography. We quantified the effects of elevation, topography and forest edge on habitat conditions and woody plant diversity of tropical montane forest fragments. Location Tropical montane forest fragments, ‘ Y ungas’, B olivia. Methods We measured microclimate and sampled soil properties and woody vegetation at forest edges and in the forest interior on ridges and in gorges along an elevational gradient of 600 m. We analysed effects of elevation, topography and forest edge on habitat conditions (i.e. microclimate, soil properties and forest structure), species richness, evenness and composition with linear mixed effects models and detrended correspondence analysis ( DCA ). Results Changes in habitat conditions were weaker along the elevational gradient than between forest interior and forest edge and between different topographies. Species richness was not affected by any gradient, while species evenness was reduced at forest edges. All three gradients affected species composition, while effects of topography and forest edge were stronger than that of elevation. Conclusions In general, effects of the 600‐m elevational gradient were weak compared to effects of forest edge and topography. Edge effects shifted species composition towards pioneer species, while topographical heterogeneity is particularly important for generating high diversity in montane forests. These results underscore that edge effects have severe consequences in montane forest remnants and that small‐scale variation between topographical microhabitats should be considered in studies that predict monotonous upslope migrations of plant species in tropical montane forests due to global warming.